On Intrinsic Information

Matthias Christandl and Renato Renner

We introduce the public Eve scenario and show that the secret key
rate in this scenario is bounded by the intrinsic information. This
elucidates previous results and gives new insights in the gap
between formation and extraction of secret information.

Intrinsic information, in its function as an upper bound on the
secret key rate, is generalized to secret key agreement from
arbitrary tripartite quantum states.